TTR S3 bump steer

[Lessen]

I'm sure some of you guys have noticed how bad the bump steer is in this thing. Did they design it that way on purpose or what? It seems to want to go wherever it wants what it takes a good bump in my backyard. I'm just curious to see if any of you have done anything to fix it?

I replaced the outside tie rods with a different pair of rod ends I had layin around. Then I installed them above the steering knuckle instead of below it. My bump steer is practically gone now. I'm not sure if this is a step forward or a step backward but I'll see when I get home today and run it around. You can doit with the stock ends but because the ball extension is so long it just barely grazes the inside of the wheel's edge.

what's your take?

 

[CorradoPsi]

not sure on the specifics of your car. but when adjusting bump steer i usually look for either zero bump steer or a slight bit of bump in.

 

[Plaidfish]

Okay can we please define the bump steer term....I hear people throw it around alot in refference to different scenarios......I understand it to mean when it's in the bumps and the supension is keeping the weight off the wheels your steering is sporadic and inconsistent.....is that how it's defined?

 

[niggle]

Okay can we please define the bump steer term....I hear people throw it around alot in refference to different scenarios......I understand it to mean when it's in the bumps and the supension is keeping the weight off the wheels your steering is sporadic and inconsistent.....is that how it's defined?

The conventional understanding of bump-steer is the effect caused by toe-in/out changing when the front suspension is at the extremes of compression/droop. Usually, extreme toe-out occurs and the car will dart from side to side.

It might be worth checking to see that the front suspension is not binding and that the damper oil is not too heavy. Both would prevent the suspension from returning quickly to its normal ride height and wheel alignment.

 

[CorradoPsi]

niggle is right. bump steer is the change in toe under suspension compression and rebound. bump in makes a car more stable and easy to drive. bump out makes the car more aggressive, but less controllable.

 

[Lessen]

the above statements are correct. When the car's front suspension is fully active (compressed), it creates more toe-in (in my case that is). The term is misleading because it really doesn't have anything to do with the car actually steering, however the action that is created is caused by the steering setup. I don't know if steering design is the same in all cars, but for the sake of conversation I will assume it is. genrally you have a slider that is attached to two "tie rods". one on each end, the outside ends of those are attached to the steering knuckle. The angle of the tie rod is what is important here. Let's assume that a car is still and the suspension is not active, in some setups the tie rod may be at an angle, that is to say the end at the knuckle may be lower than the end at the slider. Think of a hand of a clock pointed toward the 4. Now when you compress the suspension that linkage is going to level out... like the hand on the clock points to the 3. The difference is that when the linkage is in this position the overal lateral (sideways) distance of the tie rod is greater. This in turn pushes the knuckle out and effectively changes the wheels angle.

I can see how this can be good but I just think it's a bit excessive in this particular car. I was curious what other S3 owners think. right now it's shows just a tad amound of toe-out bump. I would prefer it to be zero or slightly in, but I'll have to play around with it. If I use the same rod ends except put them back underneath the knucle I should get some toe-in bump but not as much as stock form. I'll run it here in a little while and see how I like it.

 

[Plaidfish]

Okay I see...I knew it was a change in the toe and / or camber I did'nt know how they affected the control.....thanks guys....I had a problem w/ my T-maxx doing that...turns out I had the turnbuckles on wrong.....DOH

 

[mikeburgin]

cannot quite work out how using different tie rods will change your bump steer aposed to the original ones, since to acheive the same toe out angles your tie rods will be the same lenght, normally altering the bump steer is done by raising or lowering the "slider" by using shims between the servo saver and arm, as its the height of this that gives you varying degrees of bump steer

 

[Plaidfish]

I had them sitting on top of the knuckle arm instead of the bottom...I guess it was more of a severe toe in than Bump steer....

 

[Lessen]

cannot quite work out how using different tie rods will change your bump steer aposed to the original ones, since to acheive the same toe out angles your tie rods will be the same lenght, normally altering the bump steer is done by raising or lowering the "slider" by using shims between the servo saver and arm, as its the height of this that gives you varying degrees of bump steer

it's not the rod or the rod ends tha made the difference. I installed the rod above the knuckles instead of beneath them. That would be the same as lowering the slider as you mentioned. The reason I talked about using different rod ends is because the stockers will make slight contact with the wheel in this position. the stock end has a ball that is extended on one end. otherwise I would need to cut or grind it off.

After running it yesterday I found it to be much more predictable in it's manner, I may do a little bit of adjusting but I like it a lot more now.